src/Lucene.Net.QueryParser/Flexible/Standard/Processors/PhraseSlopQueryNodeProcessor.cs

using Lucene.Net.QueryParsers.Flexible.Core.Nodes;
using Lucene.Net.QueryParsers.Flexible.Core.Processors;
using Lucene.Net.QueryParsers.Flexible.Standard.Nodes;
using System.Collections.Generic;

namespace Lucene.Net.QueryParsers.Flexible.Standard.Processors
{
    /*
     * Licensed to the Apache Software Foundation (ASF) under one or more
     * contributor license agreements.  See the NOTICE file distributed with
     * this work for additional information regarding copyright ownership.
     * The ASF licenses this file to You under the Apache License, Version 2.0
     * (the "License"); you may not use this file except in compliance with
     * the License.  You may obtain a copy of the License at
     *
     *     http://www.apache.org/licenses/LICENSE-2.0
     *
     * Unless required by applicable law or agreed to in writing, software
     * distributed under the License is distributed on an "AS IS" BASIS,
     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     * See the License for the specific language governing permissions and
     * limitations under the License.
     */

    /// <summary>
    /// This processor removes invalid <see cref="SlopQueryNode"/> objects in the query
    /// node tree. A <see cref="SlopQueryNode"/> is invalid if its child is neither a
    /// <see cref="TokenizedPhraseQueryNode"/> nor a <see cref="MultiPhraseQueryNode"/>.
    /// </summary>
    /// <seealso cref="SlopQueryNode"/>
    public class PhraseSlopQueryNodeProcessor : QueryNodeProcessor
    {
        public PhraseSlopQueryNodeProcessor()
        {
            // empty constructor
        }

        protected override IQueryNode PostProcessNode(IQueryNode node)
        {
            if (node is SlopQueryNode phraseSlopNode)
            {
                if (!(phraseSlopNode.GetChild() is TokenizedPhraseQueryNode)
                    && !(phraseSlopNode.GetChild() is MultiPhraseQueryNode))
                {
                    return phraseSlopNode.GetChild();
                }
            }

            return node;
        }

        protected override IQueryNode PreProcessNode(IQueryNode node)
        {
            return node;
        }

        protected override IList<IQueryNode> SetChildrenOrder(IList<IQueryNode> children)
        {
            return children;
        }
    }
}